Benzodiazepine drugs are among the most widely prescribed of all medications, and there is increasing concern about misuse and abuse of these compounds. This project will investigate the reinforcing, discriminative stimulus, and physiological-dependence producing properties of benzodiazepine-like drugs in baboons and rats. Three interrelated sets of experiments will be conducted. One set of experiments will use drug self-administration procedures. Two experiments will investigate various environmental and pharmacological factors which may enhance and/or modulate intravenous benzodiazepine self-administration, while another study will compare the oral self-administration of a series of benzodiazepines. A second set of experiments will use drug discrimination procedures. These studies will explore molecular mechanisms of action of benzodiazepine-like drugs and characterize interactions between benzodiazepines and opioids. The third set of experiments will use antagonist precipitated withdrawal procedures to help characterize physiological dependence on and mechanisms of action of benzodiazepine-like drugs. Overall, the experiments will provide information relevant to the abuse/dependence liability and behavioral, pharmacological, and molecular mechanisms of action of benzodiazepine-like drugs. More generally, scientific characterization of the benzodiazepine-like compounds will provide information concerning the major health problems of drug abuse. Data from this project will ultimately have clincal relevance in the treatment and prevention of drug abuse.